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Chapter 10 Marine Fishes

Chapter 10 Marine Fishes. Fishes and Other Vertebrates. Fishes are vertebrates—animals that possess vertebrae, a series of bones or cartilages that surround the spinal cord and help support the body Primitive fishes lacked paired fins and jaws

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Chapter 10 Marine Fishes

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  1. Chapter 10 Marine Fishes

  2. Fishes and Other Vertebrates • Fishes are vertebrates—animals that possess vertebrae, a series of bones or cartilages that surround the spinal cord and help support the body • Primitive fishes lacked paired fins and jaws • Adaptation of jaws and paired fins allowed fish to more efficiently obtain food ultimately replacing all but a few jawless forms.

  3. Jawless Fishes • Hagfish - lampreys • Lack both jaws and paired appendages • Have skeletons of cartilage (no bone) • Lack scales • Hagfish also lack vertebrae

  4. Hagfishes • Bottom dwelling “slime eels” • Skins are used to make leather goods • Slime glands produce abundant milky, gelatinous fluid for protection if hagfish is disturbed

  5. Lampreys • Have oral disk and rasping tongue covered with horny dentacles to grasp prey, rasp hole in the body and suck out tissue and fluid.

  6. Cartilaginous Fishes • Class Chondrichthyes • e.g. sharks, skates, rays, chimaeras • Skeleton of cartilage • Possess jaws and paired fins • Placoid scales cover skin

  7. Sharks • Top predators of ocean’s food webs • Excellent swimmers with streamlined bodies • swim with powerful, sideways sweeps of the caudal fin (tail) • heterocercal tail: caudal fin in which the dorsal lobe is longer than the ventral • Males have claspers—modified pelvic fins which transfer sperm from the male to the female

  8. Dorsal fin Kidney Rectal gland Spine Caudal fin Spleen Stomach Gill slits Testis Mouth Heart Pharynx Intestine Pancreas Clasper Pelvic fin Liver Cloaca Pectoral fin Placoid scales Stepped Art Fig. 10-3, p. 266

  9. Sharks • Ventral mouth with multiple rows of teeth which are constantly replaced • Found in all oceans with the greatest numbers in temperate and tropical waters • Humans exploit shark populations for fins, meat, oil, leather, cartilage and sport

  10. Skates and Rays • Have flattened bodies adapted to a bottom existence • Greatly enlarged pectoral fins that attach to the head • Reduced dorsal and caudal fins • Eyes and spiracles (openings for the passage of water) on top of the head • Gill slits on the ventral side • Lack anal fin • Specialized teeth are used to crush prey (e.g. benthic invertebrates)

  11. Skates and Rays • Electric rays have electric organs that can deliver up to 220 V • Stingrays have hollow barbs connected to poison glands • treatment for stingray wounds: submerge in hot water to break down protein toxin • Sawfishes and guitarfishes have a series of (non-venomous) barbs along their pointed rostrums • Fished commercially for food, many are considered threatened

  12. Lobefins • Coelacanths – classified as lobefins due to presence of rod-shaped bones surrounded by thick muscle in the pelvic and pectoral fins • Only known as fossils until discovery of living specimen in 1938

  13. Lobefins • Live in Indian Ocean at depths of 150 to 250 meters • Skeleton made of bone and cartilage (vertebral column is cartilage) • Rostral organ in head detects weak electrical currents, may aid in prey detection • Life span is 60 years, reach sexual maturity at ~ 20 years, produce 5 to 26 live young • Considered to be in danger of extinction

  14. Ray-Finned Fishes • Possess unpaired and paired fins, providing better control of movements • 1 or more dorsal fins, caudal fin, and usually anal fin • help maintain stability while swimming • Paired fins consist of pectoral and pelvic fins • both used in steering • pectoral fins also help to stabilize the fish

  15. The Biology of Fishes: Body Shape • Shape of body determined by characteristics of habitat • Fusiform body shape: streamlined shape with a very high and narrow tail • efficient movement for active swimmers

  16. Body Shape • Laterally compressed or deep body • allows navigation through complex habitat, e.g., grass or corals

  17. Body Shape • Depressed or flattened bodies • bottom-dwelling fishes

  18. Body Shape • Globular bodies, enlarged pectoral fins • appropriate for sedentary lifestyle

  19. Body Shape • Long, snake-like bodies, absent or reduced pelvic and pectoral fins • useful for burrowing, living in tight spaces

  20. Fish Coloration and Patterning • Countershading is seen in open ocean fish • when viewed from above, dark color blends in with surrounding water; when viewed from below, white belly blends in with lit surface waters • Disruptive coloration—background color of the body is usually interrupted by vertical lines; may be a dark dot (“eyespot”) present in tail area • more difficult for predators to see the fish

  21. Fish Coloration and Patterning • Poster colors: bright, showy color patterns • may advertise territorial ownership, aid foraging individuals to keep in contact, or be important in sexual displays • warning coloration: bright coloration to warn predators that the fish is too venomous or spiny to eat

  22. Fish Coloration and Patterning • Cryptic coloration: coloration which blends with the environment • used for camouflage

  23. Locomotion • muscles contract alternately from one side of the body to the other

  24. Locomotion • Fish with different body forms swim in different ways • elongate fish undulate the entire body • swift swimmers flex only the posterior portion of the body • other fish are somewhere in between • fish with a dermal skeleton can only flex the area before the caudal fin • some fish swim using their fins alone without body flexure

  25. The Biology of FishesRespiration and Osmoregulation • Gills often used to extract O2, eliminate CO2, and aid in salt balance • gill filaments: highly vascularized, rod-like structures which compose the gills

  26. Operculum (gill cover) Gill filaments Gill rakers Oxygenated blood leaving gill Water + O2 Gill filament Water + CO2 Deoxygenated blood entering gill Deoxygenated blood entering gill Water and CO2 Blood flow Blood capillaries Water and O2 Stepped Art Fig. 10-21, p. 278

  27. Respiration and Osmoregulation • Water must be continuously moved past the gills to keep blood oxygenated • most ray-finned fishes ventilate gills by pumping water across them using gill pumps • very active fishes, e.g., sharks, tuna, and swordfish use ram ventilation—continuously swimming forward at high velocity with the mouth open

  28. Respiration and Osmoregulation • Osmoregulation refers to process by which organisms maintain proper concentration of solutes and water in body fluids • Blood’s salt concentration is about 1/3 that of seawater, so water is lost • Fish drink seawater to compensate

  29. Salt-excreting gland Salts diffuse in through gills Some salt water swallowed with food Kidney with large glomeruli— reabsorbs urea Gains salts by diffusion Drinks salt water Salt excreted through gills Kidney with small or no glomeruli Water gain by osmosis Large volume of hypotonic urine Water loss by osmosis Small volume of isotonic urine Stepped Art Fig. 10-22, p. 279

  30. The Biology of FishesCardiovascular System • Consists of heart, arteries, veins, and capillaries

  31. Cardiovascular System • maintain body-core temperature at 2-10oC above seawater, increasing efficiency of swimming muscles

  32. The Biology of FishesBuoyancy Regulation • Maintaining buoyancy • sharks sink if they stop swimming • large livers produce squalene—an oily material with a density less than seawater

  33. Buoyancy Regulation • Most fish use a swim bladder—a gas-filled sac that helps offset the density of the body and regulates buoyancy • the fish can adjust the amount of gas in the swim bladder to maintain depth

  34. Buoyancy Regulation • Active swimmers do not have swim bladders, and must swim to avoid sinking • Bottom dwelling fish lack swim bladder, do not need to maintain buoyancy in water column

  35. The Biology of FishesNervous System and Senses • Nervous system consists of: brain, spinal cord, peripheral nerves, and various sensory receptors • Olfaction and Taste • olfactory receptors in sharks (“swimming noses”) well developed • ray-finned fishes have olfactory pits—blind sacs opening to the external environment that contain olfactory receptors • taste receptors may be located on the surface of the head, jaws, tongue, mouth and barbels (whisker-like processes about the mouth)

  36. Nervous System and Senses • Lateral line system and hearing • ray-finned fishes have a lateral line system for detecting movement in the water – aids in locating prey and avoiding predators • lateral lines consist of canals running along the length of the fish’s body and over the head

  37. Nervous System and Senses • Lateral line system and hearing • ears are internal and have a detection range of 200 to 13,000 hertz • human range = 20 to 20,000 hertz

  38. Nervous System and Senses • Vision • no eyelids (or poorly developed) • usually don’t need to adjust pupil size because of the low quantity of light • eyes are usually set on the sides of the head • shallow-water species can perceive color

  39. Nervous System and Senses • Ampullae of Lorenzini • organs scattered over the top and sides of shark (and relatives) head • sense electrical currents in water

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